PNG Metadata to JSON

How PNG metadata extraction works

A PNG file is a fixed 8-byte signature followed by a sequence of length-prefixed chunks ([4-byte length][4-byte type][data][4-byte CRC]). Alongside required chunks like IHDR (dimensions, bit depth, color type) and IDAT (pixel data), encoders and editors often embed free-text metadata in three optional chunk types: tEXt (plain Latin-1 key/value pairs, e.g. Author or Description), zTXt (the same, zlib-compressed), and iTXt (UTF-8 text that supports international keywords and can optionally be compressed too). This tool reads the raw bytes of your file with a DataView, walks the chunk list, and decodes any text chunks it finds — using the browser's native DecompressionStream("deflate") API to inflate the zlib-compressed chunks — then serializes everything to JSON. It uses the same low-level binary-parsing approach as the EXIF Viewer, just applied to PNG's chunk format instead of JPEG's marker segments. Common places to find embedded PNG text metadata include screenshots (software/OS info), AI-generated images (prompt/model parameters), and files exported from design tools (author, copyright, or software comments).